Phased array radar antennas are generally known and implemented. Phased array antennas include apertures formed from a multitude of radiating elements. Each element is individually controlled in phase and amplitude. In this manner, desired radiating patterns and directions may be achieved. By rapidly switching the elements to switch beams, multiple radar functions may be realized.
Referring now to FIG. 1, there is shown a conventional transmit/receive switching circuit arrangement 100 for a phased array radar antenna. Circuit 100 includes a microstrip coupled to an input terminal P1 and to a transmit terminal P3 and capacitors 120, 130. “Microstrip”, as used herein, generally refers to a transmission line used for transmitting high frequency signals, such as radio frequency or microwave frequency signals. A microstrip may typically take the form of a thin, strip-like transmission line mounted on a flat dielectric substrate, that is in-turn mounted on a ground plane. Capacitors 120, 130 are coupled to a receive terminal P2, a bias terminal BIAS, and ground through radio frequency (RF) diodes 140, 150. Transmit terminal P3 is coupled to a waste load 110.
When a sufficiently positive bias BIAS is provided, diodes 140, 150 essentially provide short-circuit conditions, such that signals are steered from input terminal P1 to transmit terminal P3 and hence waste load 110. When a sufficiently negative bias BIAS is provided, diodes 140, 150 essentially provide open circuit conditions, such that signals are steered to receive terminal P2. Circuitry 100 and its operation are generally known in the phased-array radar arts.
However, such a configuration and operation undesirably introduces signal losses, due to the incorporation of wires, jumpers and materials that affect RF performance and compromise circuit performance. Accordingly, it is desirable to eliminate these wires, jumpers and materials, such as those associated with the depicted diodes, while maintaining selective transmit and receive functionalities.